Research on the Formation Mechanism and Distribution Characteristics of Surface Roughness in End Milling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Title: Research on the Formation Mechanism and Distribution Characteristics of roughness of surface in End Milling
Journal: Journal of Manufacturing and Materials Processing (JMMP)
Recommendation: Major Revision

This manuscript investigates the formation mechanism and distribution characteristics of surface roughness in end milling, specifically focusing on the effects of tool radial deflection and axial strain. The authors derived a mathematical expression for the axial strain at the tool tip using a two-segment cantilever beam model, which is subsequently validated through slot and half-slot milling experiments. Correlating the horizontal/radial cutting force with the tool tip's axial strain to explain the non-uniform distribution of surface roughness is an interesting approach. Nevertheless, the manuscript requires substantial improvements in theoretical rigor, experimental consistency, and language presentation before it can be considered for publication.

Comments and Recommendations:

1. Theoretical Formulation:The fundamental premise of the paper attributes surface roughness primarily to the axial strain (Δaz) induced by tool deflection. However, classical metal cutting theory establishes that theoretical surface roughness is predominantly dictated by kinematic parameters (e.g., feed per tooth, tool nose radius) and system dynamics/vibrations. The authors must rigorously explain how Δaz couples with or overrides this traditional kinematic roughness profile.
2. Terminology:The term "level machining force" is non-standard. The universally recognized terminology is "horizontal cutting force" or "radial-tangential resultant force in the X-Y plane". Please rectify this throughout the entire manuscript.
3. Mathematical Approximation:In Equation (14), the small-angle approximation sin(α)≈α is utilized. While mathematically valid for negligible angles, the authors should quantitatively evaluate the exact contribution of this micro-strain to the overall surface roughness (typically on the micrometer scale) and compare it with the theoretical kinematic roughness to substantiate its relative significance.
4. Experimental Consistency:The experimental design exhibits a critical lack of consistency. Specifically, groove milling (Section 3.1) was conducted on #45 steel at a spindle speed of 900 rpm, whereas semi-groove milling (Section 3.2) utilized AISI 321 stainless steel at 8000 rpm. The authors must explain the rationale behind using completely different materials and cutting parameters, as this discrepancy severely undermines the ability to draw unified, generalized conclusions.
5. Statistical Reliability:Measuring surface roughness from a single experimental pass per condition lacks statistical reliability, particularly given the "important fluctuations" mentioned in the authors' conclusion. To ensure the repeatability and robustness of the results, error bars must be incorporated into Figures 10, 13, and 15, reflecting data from multiple repetitions (at least three trials per condition).
6. Academic Terminology:The phrase "roughness of surface" should be replaced with the standard academic term "surface roughness" throughout the text.
7. Statistical Expression:The authors frequently use the word "important" to imply statistical relevance (e.g., "is importantly higher", "not very important"). The scientifically accurate terminology for such contexts is "significant" or "significantly".
8. Title Revision:It is recommended to revise the title to: "Research on the Formation Mechanism and Distribution Characteristics of Surface Roughness in End Milling".
9. Abstract Corrections:Please replace "level machining force" with "horizontal cutting force", "press strain" with "compressive strain", and "machined exterior" with "machined surface".
10. Citation Format:In the Introduction, several citations lack proper contextual integration. For instance, phrasing such as "Chen C., Wu C., Zhang T., et al. [1] used..." should be appropriately formatted to "Chen et al. [1] utilized...".
11. Figure Quality:Figures 1, 2, and 3 are overly rudimentary. Please redraw these schematics using professional CAD or illustration software to meet the publication standards of an international journal.
12. Modeling Assumptions:In Equation (1), h(θ) is defined as the instantaneous uncut chip thickness. The formula h(θ)=fzsin(θ) generally applies to straight-tooth cutters. For helical end mills, the axial engagement and helix angle play crucial roles. The authors must provide a strong justification for neglecting the helix angle in their current model.
13. Typographical Errors:In Tables 1 and 3, "per-tooth feed rate AA " is a typo and should be corrected to standard notation, such as fz .
14. Image Resolution:The text and labels in Figures 8 and 11 are blurry. Please provide high-resolution versions of these images (minimum 300 dpi).
15. Language and Formatting:The manuscript contains awkward phrasing, grammatical inaccuracies, and "Chinglish" expressions. It is strongly advised that the authors seek assistance from a professional English editing service or a native speaker to thoroughly proofread and polish the manuscript.

Comments on the Quality of English Language

The manuscript contains awkward phrasing, grammatical inaccuracies, and "Chinglish" expressions. It is strongly advised that the authors seek assistance from a professional English editing service or a native speaker to thoroughly proofread and polish the manuscript.

Author Response

All comments have been addressed in the attached document. Please refer to the file for details. Wishing you a pleasant life and good health.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript adopts theoretical and experimental methods to study on the formation mechanism and distribution Characteristics of surface roughness in end milling, and the structure of the paper is reasonable. Before it can be accepted, the following issues need to be addressed.

1. Please modify the title of the manuscript from “roughness of surface” to “surface roughness”.
2. Please pay attention to the standardization of paper writing. For example, when citing references, "Chen C., Wu C., Zhang T., et al." in the original manuscript should be changed to "Chen et al.". Please revise the entire text regarding this issue.
3. The authors are suggested to add a paragraph at the end of the "Introduction" section, introducing the main research content and the structure of the paper.
4. In the theoretical derivation of Section 2, the characteristics of the processed material, such as elastic deformation and recovery, were not considered. How did the authors address this issue?
5. In Section 3, the authors said both of Equations (3) and (15) established the relationship between the processed roughness of surface and cutting variables, which is confusing. Equation 3 is the mathematical formula for the instantaneous level machining force and Equation 15 is the axial tensile strain Δaz of the cutting edge. The axial tensile strain Δaz of the cuttingedge was used to characterize the roughness of the processed surface. What is the quantitative relationship between surface roughness andΔaz?
6. There are many characterization indicators for surface roughness, such as Ra, Rz, etc. Please clarify which indicator is referred to in the theoretical derivation of this manuscript.
7. In this study, it was established a mathematical expression of axial strain on the tip of cutting edge under level machining force, and this axial strain was used to represent the processed surface roughness. What is the significance of this research conclusion in guiding the process? Please clarify.
8. The first paragraph of the conclusion should be discussed in section 3. The conclusion section should be a summary of the entire content. Please clarify the limitations and engineering implications of this study in the conclusion.

Author Response

All comments have been addressed in the attached document. Please refer to the file for details.

Wishing you a pleasant life and good health.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper has potential findings for the publication. However, following few points need to be addressed:

1. The literature review is rather sparse for a research paper. Furthermore, most of the analyzed works are older than five years. The "Introduction" chapter should be enriched with an analysis of more recent papers.
2. What was the reason for using a very long and slender cutter holder? Did the authors of the article consider that holder length affects the rigidity of the tool set and therefore the resulting sorface roughness?
3. In Table 4, the authors present the results of the effect of cutting depth on surface roughness. A cutting depth of 0.3 mm yielded the highest surface roughness value. So why was a cutting depth of 0.3 mm retained in further research? Were the researchers interested in obtaining higher Ra values?
4. How do the authors of the paper explain the increase in surface roughness with increasing cutting depth?
5. The paper should include the exact name of the tool and its manufacturer.
6. Was a coolant used in the tests? If so, please provide its name and manufacturer.
7. Why did the authors focus on the surface roughness parameter Ra? The paper presents isometric maps, so it was possible to obtain values ​​for parameters such as Sa, Sq, Sz, Sv, and Sp. These parameters better characterize the surface than the Ra parameter.

Author Response

All comments have been addressed in the attached document. Please refer to the file for details.

Wishing you a pleasant life and good health.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I have thoroughly reviewed your revised manuscript and all the point-by-point response letters submitted in this resubmission. All the questions and concerns I raised in the previous review round have been fully addressed, the supplemented experimental data is rigorous and sufficient, the logical contradictions in the original discussion section have been reasonably revised, and the overall presentation of the manuscript has reached the publication standards of this journal.

I am very satisfied with your revision work and recommend that this manuscript be accepted for publication in its current form.

Author Response

Thank you for your positive feedback on the revised draft. Wishing you all the best and good health.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript has been well revised.

Author Response

  Thank you for your positive recognition of the revised manuscript. We wish you all the best and good health.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have significantly improved their work.

However, the name of the milling cutter used in the research was not provided. This name should be provided in the manuscript.

Once this information is provided, the article can be published.

Author Response

  All comments have been addressed in the attached document. Please refer to the file for details. Wishing you a pleasant life and good health.

Author Response File: Author Response.pdf